﻿using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Text;

namespace System.IO {
	public static class FileUtils {
		public static readonly List<string> Directories = new List<string>();
		private const uint STGM_READ = 0;
		private const int MAX_PATH = 260;

		[DllImport("shfolder.dll", CharSet = CharSet.Auto)]
		private static extern int SHGetFolderPath(IntPtr hwndOwner, int nFolder, IntPtr hToken, int dwFlags, StringBuilder lpszPath);

		[Flags]
		private enum SLGP_FLAGS {
			/// <summary>Retrieves the standard short (8.3 format) file name</summary>
			SLGP_SHORTPATH = 0x1,
			/// <summary>Retrieves the Universal Naming Convention (UNC) path name of the file</summary>
			SLGP_UNCPRIORITY = 0x2,
			/// <summary>Retrieves the raw path name. A raw path is something that might not exist and may include environment variables that need to be expanded</summary>
			SLGP_RAWPATH = 0x4
		}

		[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
		private struct WIN32_FIND_DATAW {
			public uint dwFileAttributes;
			public long ftCreationTime;
			public long ftLastAccessTime;
			public long ftLastWriteTime;
			public uint nFileSizeHigh;
			public uint nFileSizeLow;
			public uint dwReserved0;
			public uint dwReserved1;
			[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
			public string cFileName;
			[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 14)]
			public string cAlternateFileName;
		}

		[Flags]
		private enum SLR_FLAGS {
			/// <summary>
			/// Do not display a dialog box if the link cannot be resolved. When SLR_NO_UI is set,
			/// the high-order word of fFlags can be set to a time-out value that specifies the
			/// maximum amount of time to be spent resolving the link. The function returns if the
			/// link cannot be resolved within the time-out duration. If the high-order word is set
			/// to zero, the time-out duration will be set to the default value of 3,000 milliseconds
			/// (3 seconds). To specify a value, set the high word of fFlags to the desired time-out
			/// duration, in milliseconds.
			/// </summary>
			SLR_NO_UI = 0x1,
			/// <summary>Obsolete and no longer used</summary>
			SLR_ANY_MATCH = 0x2,
			/// <summary>If the link object has changed, update its path and list of identifiers.
			/// If SLR_UPDATE is set, you do not need to call IPersistFile::IsDirty to determine
			/// whether or not the link object has changed.</summary>
			SLR_UPDATE = 0x4,
			/// <summary>Do not update the link information</summary>
			SLR_NOUPDATE = 0x8,
			/// <summary>Do not execute the search heuristics</summary>
			SLR_NOSEARCH = 0x10,
			/// <summary>Do not use distributed link tracking</summary>
			SLR_NOTRACK = 0x20,
			/// <summary>Disable distributed link tracking. By default, distributed link tracking tracks
			/// removable media across multiple devices based on the volume name. It also uses the
			/// Universal Naming Convention (UNC) path to track remote file systems whose drive letter
			/// has changed. Setting SLR_NOLINKINFO disables both types of tracking.</summary>
			SLR_NOLINKINFO = 0x40,
			/// <summary>Call the Microsoft Windows Installer</summary>
			SLR_INVOKE_MSI = 0x80
		}


		/// <summary>The IShellLink interface allows Shell links to be created, modified, and resolved</summary>
		[ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("000214F9-0000-0000-C000-000000000046")]
		private interface IShellLinkW {
			/// <summary>Retrieves the path and file name of a Shell link object</summary>
			void GetPath([Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszFile, int cchMaxPath, out WIN32_FIND_DATAW pfd, SLGP_FLAGS fFlags);
			/// <summary>Retrieves the list of item identifiers for a Shell link object</summary>
			void GetIDList(out IntPtr ppidl);
			/// <summary>Sets the pointer to an item identifier list (PIDL) for a Shell link object.</summary>
			void SetIDList(IntPtr pidl);
			/// <summary>Retrieves the description string for a Shell link object</summary>
			void GetDescription([Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszName, int cchMaxName);
			/// <summary>Sets the description for a Shell link object. The description can be any application-defined string</summary>
			void SetDescription([MarshalAs(UnmanagedType.LPWStr)] string pszName);
			/// <summary>Retrieves the name of the working directory for a Shell link object</summary>
			void GetWorkingDirectory([Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszDir, int cchMaxPath);
			/// <summary>Sets the name of the working directory for a Shell link object</summary>
			void SetWorkingDirectory([MarshalAs(UnmanagedType.LPWStr)] string pszDir);
			/// <summary>Retrieves the command-line arguments associated with a Shell link object</summary>
			void GetArguments([Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszArgs, int cchMaxPath);
			/// <summary>Sets the command-line arguments for a Shell link object</summary>
			void SetArguments([MarshalAs(UnmanagedType.LPWStr)] string pszArgs);
			/// <summary>Retrieves the hot key for a Shell link object</summary>
			void GetHotkey(out short pwHotkey);
			/// <summary>Sets a hot key for a Shell link object</summary>
			void SetHotkey(short wHotkey);
			/// <summary>Retrieves the show command for a Shell link object</summary>
			void GetShowCmd(out int piShowCmd);
			/// <summary>Sets the show command for a Shell link object. The show command sets the initial show state of the window.</summary>
			void SetShowCmd(int iShowCmd);
			/// <summary>Retrieves the location (path and index) of the icon for a Shell link object</summary>
			void GetIconLocation([Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder pszIconPath,
				int cchIconPath, out int piIcon);
			/// <summary>Sets the location (path and index) of the icon for a Shell link object</summary>
			void SetIconLocation([MarshalAs(UnmanagedType.LPWStr)] string pszIconPath, int iIcon);
			/// <summary>Sets the relative path to the Shell link object</summary>
			void SetRelativePath([MarshalAs(UnmanagedType.LPWStr)] string pszPathRel, int dwReserved);
			/// <summary>Attempts to find the target of a Shell link, even if it has been moved or renamed</summary>
			void Resolve(IntPtr hwnd, SLR_FLAGS fFlags);
			/// <summary>Sets the path and file name of a Shell link object</summary>
			void SetPath([MarshalAs(UnmanagedType.LPWStr)] string pszFile);

		}

		[ComImport, Guid("0000010c-0000-0000-c000-000000000046"),
		InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
		private interface IPersist {
			[PreserveSig]
			void GetClassID(out Guid pClassID);
		}


		[ComImport, Guid("0000010b-0000-0000-C000-000000000046"),
		InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
		private interface IPersistFile : IPersist {
			new void GetClassID(out Guid pClassID);
			[PreserveSig]
			int IsDirty();

			[PreserveSig]
			void Load([In, MarshalAs(UnmanagedType.LPWStr)] string pszFileName, uint dwMode);

			[PreserveSig]
			void Save([In, MarshalAs(UnmanagedType.LPWStr)] string pszFileName,
				[In, MarshalAs(UnmanagedType.Bool)] bool fRemember);

			[PreserveSig]
			void SaveCompleted([In, MarshalAs(UnmanagedType.LPWStr)] string pszFileName);

			[PreserveSig]
			void GetCurFile([In, MarshalAs(UnmanagedType.LPWStr)] string ppszFileName);
		}

		// CLSID_ShellLink from ShlGuid.h 
		[ComImport, Guid("00021401-0000-0000-C000-000000000046")]
		private class ShellLink {
		}

		/// <summary>
		/// Resolves the target file of the specified shortcut.
		/// </summary>
		/// <param name="file">The path to the shortcut to resolve.</param>
		public static string ResolveShortcut(string file) {
			ShellLink link = new ShellLink();
			((IPersistFile) link).Load(file, STGM_READ);
			// TODO: if I can get hold of the hwnd call resolve first. This handles moved and renamed files.  
			// ((IShellLinkW)link).Resolve(hwnd, 0) 
			StringBuilder sb = new StringBuilder(MAX_PATH);
			WIN32_FIND_DATAW data = new WIN32_FIND_DATAW();
			((IShellLinkW) link).GetPath(sb, sb.Capacity, out data, 0);
			string str = sb.ToString();
			return str.EndsWith(".lnk") ? ResolveShortcut(str) : str;
		}

		public static string ResolvePath(string path) {
			if (path == null)
				return null;
			path = path.Trim();
			if (path.Length == 0)
				return null;
			path = path.Replace('/', Path.DirectorySeparatorChar).Replace('\\', Path.DirectorySeparatorChar);
			string directory = Path.GetDirectoryName(Path.GetFullPath(path));
			Directories.Add(directory);
			if (File.Exists(path))
				return path;
			string temp, originalPath = path;
			for (int i = 0; i < Directories.Count; i++) {
				temp = Directories[i];
				if (path.StartsWith(Path.DirectorySeparatorChar.ToString())) {
					path = temp.EndsWith(Path.DirectorySeparatorChar.ToString()) ? temp.Substring(0, temp.Length - 1) + path : temp + path;
					if (File.Exists(path))
						return path;
				} else {
					path = temp.EndsWith(Path.DirectorySeparatorChar.ToString()) ? temp + path : temp + Path.DirectorySeparatorChar + path;
					if (File.Exists(path))
						return path;
				}
				path = originalPath;
			}
			return null;
		}
	}
}